1.2 Convection Currents and the Mantle

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Vocabulary

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Heat Transfer: The movement of energy from a warmer object to a cooler object.
Radiation: The transfer of energy through empty space.
Conduction: Heat transfer by direct contact of particles of matter.
Convection: Heat transfer by the movement of a heat fluid.
Density: Measure of how much mass there is in a volume of a substance.
Convection Current: The flow that transfers heat within a fluid.

Outline

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Introduction

• Heat Transfer
  • Three types of Heat Transfer
    • Radiation
    • Conduction
    • Convection

Radiation

• Transfer of energy through empty space
  • Ex. The Sun's rays warm the Earth's surface.
  • Heat transfer by radiation takes with no direct contact between a heat source and an object.

Conduction

• Heat transfer by direct contact of particles of matter
  • Ex. Spoon in a hot bowl of soup.
  • The particles near the bottom of the spoon vibrate faster as they are heated, so they bump into other particles and heat them too. Gradually the entire spoon heats up.

Convection

• Transfer of heat through a heated liquid
  • Ex. currents in a pot of heated water
  • caused by differences in temperature and density within a fluid
• When particles move faster, they spread apart thus occupying more space and the density decreases.
• Constant flow in heated liquid is called convection currents
• Heating and cooling of fluid, changes in the fluid's density, and force of gravity set convection currents in motion.

Convection in Earth's Mantle

• Mantle responds to heat
• Convection currents flow in the Earth's asthenosphere
  • The source of the heat is from the Earth's core and the mantle.
  • Hot columns of mantle rise through the asthenosphere
  • At the top of the asthenosphere, the hot material spreads out and pushes away the cooler material
  • The cooler material sinks back into the asthenosphere.
• Convection currents in asthenosphere have been flowing for 4 billion years.